Class X: Biology - StudiesToday.com Class 10... · Class X: Biology Chapter 2: Control ... by...

Class X: Biology

Chapter 2: Control and coordination.

Chapter Notes

Key learnings:

1) A system of control and coordination is essential in living organisms so

that the different body parts can function as a single unit to maintain

homeostasis as well as respond to various stimuli.

2) In animals, the nervous system and hormonal system are responsible

for control and coordination.

3) Neurons are specialized cells of the nervous system. They use

electrical and chemical signals for transferring information.

4) Receptors are specialized tips of the nerve fibres that collect the

information to be conducted by the nerves.

5) Nerve impulses travel in the following manner from one neuron to the

next : Dendrites Cell body Axon Nerve endings at the

tip of axon Synapse Dendrite of next neuron.

6) Chemicals released from axon tip of one neuron, cross the synapse or

neuromuscular junction to reach the next cell (neuron or muscle fibre).

7) Nerve impulses from many neurons interact to carry out the complex

process of thinking.

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8) Central nervous system and peripheral nervous system are parts of

our nervous system.

9) Central nervous system is made up of the brain and spinal cord.

10) Spinal cord controls the reflex actions and conducts messages

between different parts of the body and brain.

11) Reflex action is an automatic, rapid and immediate reaction to a

stimulus and is below the level of consciousness. No thinking is

involved in reflex action.

12) Reflex arc is the neural pathway that mediates a reflex action.

Pathway of reflex arc : Receptor Sensory neuron Relay neuron

Motor neuron Effector

13) The sensory neurons of reflex arcs synapse in the spinal cord

which then activates the spinal motor neurons without delay to

execute a quick action, especially in case of emergencies. The brain

also receives the information while the reflex action occurs.

14) The 3 main parts of the brain are forebrain, midbrain and

hindbrain.

15) The largest part of the brain, the forebrain, is the main thinking

region. It is made up of cerebrum, hypothalamus and thalamus.

Cerebellum, pons and medulla constitute the hindbrain.

16) Cerebrum is the largest part of the brain whereas the

cerebellum is the second largest part.

17)



Part of brain Function

Cerebrum Governs intelligence, thinking,

memory and other mental abilities,

voluntary actions, sensations,

emotions and speech

Hypothalamus Coordinates messages from the

autonomous nervous system, controls certain involuntary actions,

as well as the sexual and emotional

behaviour and forms an axis with the

pituitary

Thalamus Functions as major coordinating

center for sensory and motor

signaling.

Midbrain Acts as the coordinating centre

between forebrain and hindbrain;

also controls certain involuntary

movements

Cerebellum Responsible for precision and fine

control of voluntary movements as

well as maintaining posture and

equilibrium of the body

Pons Relays impulses between the lower

cerebellum and spinal cord, and

higher parts of the brain like the

cerebrum and mid brain; also

regulates respiration

Medulla Contains vital centres for controlling

blood pressure, respiration,

swallowing, salivation, vomiting,

sneezing and coughing.

18) Brain is protected by a bony box called cranium, within which

are present 3 layers of fluid-filled membranes for absorbing shock.



19) Peripheral nervous system consists of cranial nerves and spinal

nerves and assists in transmitting information between central nervous

system and rest of the body.

20) Reflex actions, voluntary actions and involuntary actions are the

various types of responses shown by the nervous system.

21) The sense organs detect changes in surroundings and pass this

information to the central nervous system, which after processing the

information, acts through the muscles.

22) `The movements of muscle tissues are brought about by the

contraction and relaxation of the contractile proteins in response to

nerve impulses.

23) Plants lack nervous and muscular system.

24) Plants respond to stimuli by showing 2 types of movements –

growth independent and growth dependent.

25) Growth independent movements are usually quicker than

growth dependent ones, and involve the use of electrochemical signals

by the plant. To achieve this movement, the plant cells change shape

by altering their water content.

26) Growth dependent movements or tropic movements are slow,

occurring either towards or away from the stimulus.

27) Tropic movements are shown in response to environmental

factors such as light, gravity, water and chemicals.



28) Plant roots are positively geotropic and negatively phototropic

whereas plant shoots are usually negatively geotropic and positively

phototropic.

29) Pollen tubes show chemotropism by growing towards the ovules.

30) In addition to electrochemical signals, plants and animals use

hormones for control and coordination.

31) Important plant hormones are auxin, gibberellin, cytokinin,

abscisic acid and ethylene.

Plant hormone Function

Auxin Cell elongation

Cytokinin Cell division

Gibberellin Growth of stem

Abscisic acid Inhibits growth

Ethylene Ripening of fruits

32) Auxin causes the bending of plant stem towards light as well as

the curling of plant tendrils around a support.

33) Animal hormones do not bring about directional growth

depending on environmental cues, but promote controlled growth in

various areas to maintain the body design.

34) The various endocrine glands in humans are hypothalamus,

pineal gland, pituitary gland, thyroid gland, parathyroid glands,

thymus, pancreas, adrenal glands, ovary (in female) and testis (in

males).



35) Some important hormones and their functions in human body:

Hormone Endocrine

gland

Function

Growth

hormone

Pituitary Regulates growth and development of body

Thyroxin Thyroid

gland

Controls carbohydrate, protein and fat

metabolism

Adrenaline Adrenal

gland

Prepares the body to deal with emergency

situations

Insulin Pancreas Regulates blood sugar levels

Testosterone Testis Causes development of sexual organs and

secondary sexual characteristics in males

Oestrogen Ovary Causes development of sexual organs and

secondary sexual characteristics in females

35) In case of flight or fight reaction to an emergency situation,

Adrenal glands release adrenaline into blood which acts on

heart and other tissues causes faster heart beat more oxygen

to muscles reduced blood supply to digestive system and skin

diversion of blood to skeletal muscles increase in breathing rate.

36) Deficiency of iodine causes goiter whereas deficiency of growth

hormone and insulin causes dwarfism and diabetes respectively.

37) Feedback mechanisms are present to regulate the hormone action.

38) Difference between nervous and endocrine system

Nervous system Endocrine system

Mode of

communication

Electrical impulses Chemical compounds



Speed of

communication

Very quick Slow

Can reach Only cells connected by

nervous system

All cells of the body

Continuity Cannot continuously

transmit impulses

Can act steadily and

persistently

Top Definitions

1) Receptors – Specialized structures at the ends of the nerve fibres that

collect the information to be conducted by the nerves, and are located

in the sense organs.

2) Gustatory receptors – Receptors present in tongue and capable of

detecting taste.

3) Olfactory receptors – Receptors present in nose and capable of

detecting smell.

4) Synapse – A specialized junction between two neurons, across which

nerve impulse passes.

5) Neuromuscular junction – The junction between a nerve fiber and the

muscle cell it supplies.



6) Nerve impulse – An electrochemical signal that travels through a

neuron in response to a stimulus.

7) Effectors – A muscle, gland, or organ capable of responding to a

stimulus, especially a nerve impulse.

8) Sensory neuron – A neuron that conducts impulses from a receptor

organ to the central nervous system.

9) Motor neuron – A neuron that conducts impulses from the central

nervous system to muscle or gland.

10) Relay neuron – A neuron which connects sensory neurons with

motor neurons in neural pathways.

11) Reflex action - An automatic, rapid, involuntary and immediate

reaction to a stimulus.

12) Reflex arc – The neural pathway that mediates a reflex action.

13) Cranial nerves – Nerves arising from the brain

14) Spinal nerves – Nerves arising from the spinal cord.

15) Tropic movements – The directional movements shown by

plants in response to environmental factors.

16) Hormone – The secretion of an endocrine gland that is

transmitted by blood to specific tissues in the body.



17) Phototropism – The movement of a plant towards or away from

light.

18) Hydrotropism – The movement of a plant either towards or

away from water.

19) Geotropism – The directional movements shown by plants in

response to gravity.

20) Chemotropism – Movement or growth of an organism or part of

an organism in response to a chemical stimulus.

21) Endocrine gland – A ductless gland that secretes hormones

directly into the bloodstream.

22) Feedback mechanism – A type of self-regulating mechanism in

which the level of one substance in body influences the level of

another.

Top diagrams



Structure of neuron

Neuromuscular junction



Reflex arc

Human brain



Plant showing phototropism

Plant showing geotropism



Endocrine glands in human male



Endocrine glands in human female



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